Looks like a good deal. The only catch is max input voltage is 23 volts DC. Full wave rectified track voltage can be 28-32VDC so use in engines and rolling stock (lighting passenger cars) is limited or requires a work around.

Pete

I bought those years ago, as Pete says, the sticking point is the max voltage.  I smoked a couple at full track voltage as you exceed their voltage ratings by 2-3 volts, apparently enough to kill them.  I still have a bunch in my parts box.

I saw those a few weeks ago and almost bought them but I found a much smaller prewired variant (fixed at 5V) on Amazon.  The small size allows you to stash them under track and hook them inline to track or a rectifier as needed.  I don't feel that inserting a rectifier between the buck converter and the track power source is a hassle.

Anthony

I use this one, and I made a little piggyback board to supply the DC, add a DCS choke, etc.  Note the hole to reach the adjustment pot, my board sits on top of the switching module.

The two boards are joined on the four corners to bring raw DC down to the switcher and then the regulated voltage back up to the interface board.  I also included a provision for half-wave with common ground and full wave for better efficiency and more power out, but requiring isolated outputs without a common ground.

ok so for those of us who don't know. what are they for.

So you all can get a chuckle, here’s a cobble job that works ok.  They are so cheap.  I purchased these a few years ago, $2.50 shipped off shore.  I have some for building lighting.

@TedW posted:

So you all can get a chuckle, here’s a cobble job that works ok.  They are so cheap.  I purchased these a few years ago, $2.50 shipped off shore.

Ted, the 23V input voltage limitation still is a problem.  If you put 18V on the input to that bridge, the converter will croak.

John, I’m sure you’re right, but I have a little over a year at 14vac on a couple, and have gotten away with it.  And as you see I have a few spares to carry me for a few more years…

These have their place, just not in trains without additional circuitry. Lots of applications on a layout with lighting or powering accessories like animated scenes.

An old ATX computer power supply with its 5 and 12v outputs could power most everyones layout coupled with these modules.

Pete

Ted; you have cornered the market on these things haha!

I agree that the 23V limitation likely makes these no good for engines or rolling stock on command track @ 18VAC. Too bad. But they still should be good for making 5VDC for Menards buildings, Miller signs, stuff like that. And the fact that they would be easy to bury in the wiring bundle should make them easy to use.

John, I recall the AC-DC conditioner boards that you designed for the D-Sun converters. I built a few and they are quite handy with those boards. It looks like you have re-designed that board since that time; some parts appear to be laid out differently than I remember?

Rod

@Rick Rubino posted:

ok so for those of us who don't know. what are they for.

Rick, did you get your answer? They are used for reducing a given DC voltage (up to 23V for this one) down to a lower value than might be needed for specific uses around the layout. Compact, and 3 Amp current handling covers a vast number of applications.

Rod

In many applications, I used a bridge rectifier, filter capacitor and fixed voltage rectifier chip (5V, 6V, 12V or 15V. Does the job and seems less costly and so much simpler. Pictured is a typical 12V unit.

Bob, for anything other than a very low power, linear regulators get pretty hot.  I use them a lot as well, but by the time you get to 50ma through a 5V TO-220 regulator with track voltage on the input (through the bridge and filter of course), it's getting quite warm.

Yes, they do get quite warm which is why I used a heatsink with the TO-220 versions. For extreme situations, I used the TO-3 case version which can handle heat better.

@gunrunnerjohn posted:

The two boards are joined on the four corners to bring raw DC down to the switcher and then the regulated voltage back up to the interface board.  I also included a provision for half-wave with common ground and full wave for better efficiency and more power out, but requiring isolated outputs without a common ground.

That's a nice little board John.  Would you mind sharing the circuit diagram that illustrates how the jumper selects full- vs half-wave?

@Rod Stewart posted:

Compact, and 3 Amp current handling covers a vast number of applications.

Take that 3A rating tongue in cheek Rod.  In truth, they won't do anything like 3A without overheating.

Here's a much larger buck module, at 2 amps it's running at 100C, when I added load to three amps, it shot up to 140C and went into thermal shutdown.  My experience with those little ones is it's more like 300-400ma before they're running really hot.  I'd be quite surprised if they did an amp without overload.

@Professor Chaos posted:

That's a nice little board John.  Would you mind sharing the circuit diagram that illustrates how the jumper selects full- vs half-wave?

No problem, I can post the Gerber files if you'd like them.

EDIT:  I see my reply crossed with GRJ's saying something similar.

I bought a bundle of these a while back.  For anyone unfamiliar with these, one noteworthy thing about the output rating is, above 12V 1.5Amps, the seller indicates that additional heat dissipation is needed.

Here are the Specifications quoted from their Amazon page:

Specifications:
Input voltage: DC 4.5 - 24V
Output voltage: integrated adjustable and fixed output, and adjustable range is 0.8 - 17V, fixed output is 1.8V, 2.5V, 3.3V, 5V, 9V, 12V, able to be chosen on the back side.
Output current: 3A max, please enhance cooling work when it is full load. When actual tested input 12V and output is 1.5A, no need to add other system.
Enable function control: yes, low electric level will stop working when high electric level is working. High electric level is 2-5V, low electric level is 0V or so.
Operating temperature: -40℃ - +85℃, industrial class, the higher the operation temperature is, and the smaller the output power is.
Conversion efficiency: 97.5%, 6.5V to 5V, 0.7A
Switch frequency: 500 KHz
Output ripple: 20 mV, 12V to 5V, 3A, 20M width
Output over-voltage protection: no
Temperature rising range at full load: 40℃
Static current: 0.85 mA
Voltage adjustment rate: ±0.5%
Dynamic response speed: 5% 200uS
Output short-circuit protection: yes, please don’t keep making it short-circuit.
Output opposite connection protection: no
Wiring method: soldering
Output method: soldering or pins
Welding hole spacing: 2.54 mm
Size: 20 x 11 x 5 mm

Well, my findings and the seller's findings are a bit different.

Hello All!
I thought that I would chime in on this subject. Although I’m just a bit over caveman level electronics expert, what about a voltage regulator? I found this adjustable regulator and I’m not sure how it works exactly but the input and output seems to be in the range that you are talking about. If they can be paralleled you could get 3 AMPS? Or this one? There seems to be many choices to control the input voltage. My apologies if I’m way off base.

@Winton248 posted:

Hello All!
I thought that I would chime in on this subject. Although I’m just a bit over caveman level electronics expert, what about a voltage regulator? I found this adjustable regulator and I’m not sure how it works exactly but the input and output seems to be in the range that you are talking about. If they can be paralleled you could get 3 AMPS? Or this one? There seems to be many choices to control the input voltage. My apologies if I’m way off base.

This would work but requires a number of other parts and then you have to assemble them. It would end up costing more in money and time.

Pete

Check around some more. These may not be as small but I got the complete package for just under $6 each, shipped. I'll be feeding them 14 vac.

Parameters:   Input voltage range: AC 5V-30V, DC 5V-50V   Output output range: DC 3.3V-33V   Output current range: up to 2.2A (the regulator chip can withstand a maximum current of 3A, can work at 3A output current for a short time   Module size: 51mm*26mm

Smaller: https://smile.amazon.com/gp/product/B076P4C42B/

Generally "tiny" and "high power" don't go together when you're doing power supplies.

Would you all be able to help me pick out something that would go from track voltage, to 9v dc?  This is part of my crazy lego to O gauge idea.  Lego motors/control work on 9 vdc, and are usually powered by a 6 pack of AAA batteries.  I would like to maintain as much lego in my locomotive design as possible but install picks for track power instead of a need to swap batteries.  and of course small is good.  Ideally it would even fit inside the battery box, but that's not an absolute requirement.

@jhz563 posted:

Would you all be able to help me pick out something that would go from track voltage, to 9v dc?  This is part of my crazy lego to O gauge idea.  Lego motors/control work on 9 vdc, and are usually powered by a 6 pack of AAA batteries.  I would like to maintain as much lego in my locomotive design as possible but install picks for track power instead of a need to swap batteries.  and of course small is good.  Ideally it would even fit inside the battery box, but that's not an absolute requirement.

How much do the motors draw? Smallest would be something you put together yourself. LM7809, two caps, full wave bridge good for 1 amp or less. There are modules on the bay but may not fit in a space occupied by 3 AAA batteries. A home brew could be made to fit. LM317 even better but requires a few more resistors to set the voltage.

Pete

I make these with a small switching board from the Far East.  Much more efficient than a linear regulator that will need a large heatsink at 1 amp from track power.  Track power in, adjustable DC out.

1" x .7" and 1/2" tall

OK, What is a buck converter and what does it do. Does it have anything to do with the currency exchange rate? ("buck" converter, get it?)

Asked by this conventionally operated railroad owner

A buck converter is a switching power supply that takes a higher voltage in and produces a lower voltage out.  The difference between a linear regulator and a buck regulator is the conversion efficiency.  The Linear regulator converts all the difference in voltages to heat, and with a significant input/output voltage differential, the regulator generates a lot of heat.  The buck regulator is much more efficient at converting the voltages and typically runs at 80-90% efficiency independent of the input/output voltage ratio.

@gunrunnerjohn posted:

A buck converter is a switching power supply that takes a higher voltage in and produces a lower voltage out.  The difference between a linear regulator and a buck regulator is the conversion efficiency.  The Linear regulator converts all the difference in voltages to heat, and with a significant input/output voltage differential, the regulator generates a lot of heat.  The buck regulator is much more efficient at converting the voltages and typically runs at 80-90% efficiency independent of the input/output voltage ratio.

Thanks gunrunnerjohn, but I still have questions;

How is this used and when is this (or any other regulator, for that matter) needed?

Any need on a conventionally powered layout?

John, if you don't know you need one, you probably don't!

@turkey_hollow_rr posted:

Parameters:   Input voltage range: AC 5V-30V, DC 5V-50V   Output output range: DC 3.3V-33V   Output current range: up to 2.2A (the regulator chip can withstand a maximum current of 3A, can work at 3A output current for a short time   Module size: 51mm*26mm

When you look at the size of the one you have, not to mention the heatsink that  was added to the switcher IC to handle 2.2 amps, one thing becomes apparent.  Considering the 3A specification of the anemic little 1/2" x 1" board under discussion here, it becomes pretty obvious that they're hopelessly overstating the capability of the little board.   There would be flames spouting from that little thing before it got to a 3A output!

@Norton posted:

How much do the motors draw? Smallest would be something you put together yourself. LM7809, two caps, full wave bridge good for 1 amp or less. There are modules on the bay but may not fit in a space occupied by 3 AAA batteries. A home brew could be made to fit. LM317 even better but requires a few more resistors to set the voltage.

Pete

I have to look up the amp draw for what I am trying to do - will have to come back with answer. - thank you

@gunrunnerjohn posted:

I make these with a small switching board from the Far East.  Much more efficient than a linear regulator that will need a large heatsink at 1 amp from track power.  Track power in, adjustable DC out.

1" x .7" and 1/2" tall

Very Cool GRJ.  I am not entirely clear - are you saying this does or does not need a heat sink?  I was think about mounting it in the battery box, but there's no air moving through there and not a lot of space.  I don't want to cook the circuit or warp the battery box from the heat.  Also, I am guessing that round hole in the bottom right of the image goes to a potentiometer to set the output voltage.  Does this need varied depending upon the input voltage or is it more set-it-and-forget-it?

@gunrunnerjohn posted:

When you look at the size of the one you have, not to mention the heatsink that  was added to the switcher IC to handle 2.2 amps, one thing becomes apparent.  Considering the 3A specification of the anemic little 1/2" x 1" board under discussion here, it becomes pretty obvious that they're hopelessly overstating the capability of the little board.   There would be flames spouting from that little thing before it got to a 3A output!

Oh yes, I posted that clip because they at least say the chip can handle 3 amps for short periods. I wouldn't bet any project of mine on that.

It was the input specs that drew me to these, I already have a 14vac power supply for my switch motors and these seem like a cheap way to get 3, 5, or 12 vdc I only need a few hundred milliamps to run four or five of these 5 vdc relays.

@gunrunnerjohn posted:

John, if you don't know you need one, you probably don't!

LOL

BUT THEN, there are a lot of trains I didn't know I needed until I saw and bought them.

@jhz563 posted:

Very Cool GRJ.  I am not entirely clear - are you saying this does or does not need a heat sink?  I was think about mounting it in the battery box, but there's no air moving through there and not a lot of space.  I don't want to cook the circuit or warp the battery box from the heat.  Also, I am guessing that round hole in the bottom right of the image goes to a potentiometer to set the output voltage.  Does this need varied depending upon the input voltage or is it more set-it-and-forget-it?

No heatsink, but I've never run more than about 500-600ma through these.  At that level, they get warm, but well within their ratings.  I have one on the bench with 18VAC in and 5V out into an 8 ohm load, my DC clamp-on is reading 590 milliamps.  After a few minutes running, the bottom board is reading 55C.  That's well within ratings, but I suspect trying to get more than 750-800 milliamps out of them would be over the top without additional cooling.

@Rod Stewart posted:

Just thought I would share what may be the smallest buck converters yet offered. Each is only 11 x 17 mm and is rated at up to 3 Amps, fully adjustable. It could easily be soldered inline and sleeved with a piece of 3/4" shrink sleeve to enable putting it just about anywhere. They are sold by a US seller and a card of 10 cost $7 including shipping. These took only 6 days to arrive in AZ, but state tax kicked my cost up a little.

Like most these are only good for DC, so you would still need a rectifier and filter cap on the input if you are using AC. But still you can't beat the size, and you can't build them for this price.

Rod

Rod, I have 200 of these that I had to find a way to get some use out of them and had already installed them in around 20 passenger cars when John warned me. If the load is low they work for a while. What I did was to add a pair of 1a 200v diodes between the output of the bridge and the input of the regulator board. 50v or 100v would have worked. I put one on each side + and - however they could go in a series on either the + or - side just keep the polarities correct.  The voltage drop through two diodes is just enough to lower the RMS voltage going to the board enough to keep from frying it. 1a diodes are cheap and you could use 3~ 4 diodes if you want but two are working fine on my passenger cars.  I put the Capacitor after the added diodes but it could go on before or after.    The slightly larger regulator board that John pointed out does not require the extra diodes in addition to the bridge. They tend to be a bit more expensive, though I bought 100 of them three months ago for $0.58 each.           j

You could use a Zener diode of the right rating and only need one.

The regulator boards I use have a 28V rating, marginal, but sufficient for 18-19V AC track power.  Normally, I see around 25 VDC after the bridge.  I still have 20-25 of those little boards somewhere, but I relegated them to a "Misc Parts Junkbox" after I blew a couple of them up.